Self-reported pain is a big problem because it is difficult to interpret and may be impaired or not even possible, as in young children or the severely ill. The authors of this paper tackle this problem by developing a computer vision system that automatically recognizes acute pain.
To achieve their goal, adult patients with rotator cuff injury were video-recorded while a physiotherapist manipulated their affected and unaffected shoulder. From these ratings, sequences were categorized as no-pain (rating of 0), pain (rating of 3, 4, or 5), and indeterminate (rating of 1 or 2). And a facial expresion detector were implemented, as can be seen in the figure below.
